Automatic blood pressure recorder



J 1945. w. E. GILSON 2,379,573

AUTOMATIC BLOOD PRESSURE RECORDER 2 Sheets-Sheet 1 Filed Aug. 17, 1942 'Invenfir rrerzE Gila I "6 35 July 3, 1945. w, 5150 2,3795573 I AUTOMATIC BLOOD PRESSURE RECORDER Fi1ed Aug. 17, 1942 2 Sheets-Sheet 2 J9 OGOOOOOOOOO InvenZZ/r 4 4 lflrrenE 621F411 Patented July 3, 1945 AUTOMATIC BLOOD PRESSURE RECORDER Warren E. Gilson, Madison, Wis., assignor to weconsin Alumni Research Foundation, Madison, Wis., a corporation of Wisconsin Application August 17, 1942, Serial No. 455,139

6 Claims.

My invention relates to improvements in means for the determination of blood pressure, and the primary object of my invention is to automatically determine and record blood pressure at predetermined intervals without manual intervention.

A further object is to minimize discomfort to the patient by suddenly and automatically relieving the patient of cuii pressure between pe riods of blood pressure determinations.

A further object is to provide an accurate simultaneous record of the cuff pressure and the sounds produced by the excursion of the artery walls, which indicate the blood pressures in relation to the cufi" pressure.

These and other objects of my invention are accomplished by the provision of recording means responsive to pressure and sound, and automatically timed to operate at regular intervals.

Referring to the accompanying drawings which illustrate one embodiment of my invention,

Fig. l is aview illustrating diagrammatically the various mechanisms or instrumentalities for recording pressures and sounds, together with the circuit for controlling the operation and timing of these mechanisms;

Fig. 2 is an enlarged view of a portion of the moving record chart showing the manner in which the records are marked upon the chart;

Fig. 3 is a view of the arcuate device used in connection with the chart record for reading the recorded pressures; and

Fig. 4 is a transverse sectional view on the line 44 of Fi 3.

The device is provided with an inflatable cuff A of the usual type, which is applied to the patients arm and which is connected to an airline I. Thi air line is connected at its end 2 to a suitable source of compressed air, and at its other end it is open to the atmosphere. A manually operated pressure reducing valve 3 is provided in the line for regulating the maximum desired pressure admitted to the cuff, this pressure being adjusted to a pressure well above the systolic blood pressure of the patient. On each side of the cun' connection is a suitable valve. The valve V when open, admits air pressure to the inflatable cuff; and the valve V when open, exhausts air from the cufi to the atmosphere to completely deflate the cufi. These valves are operated by electromagnets V and V res ctively, and are controlled as hereinafter des bed. A bleeder valve V preferably in the form of a manually adjustable needle valve, is connected in the line between the valves V and W for the The cuif pressure is recorded by a suitable recording mechanism. In the drawing, this recording mechanism consists of a moving chart C upon which a record is marked by a pen 5 carried on an arm 6 which is pivoted at I above the chart. The pen marker is actuatedby a bellows 8 which is connected by a link 9 to the other endof the pen .marker 50 as to swing the pen marker in an arc across the chart. 7

. The bellows is connected by an air line ID to the air line i between the two valves V and V, so that it will be responsive to the pressure in the cufi'. The chart consists of a continuous strip or band of paper which is moved longitudinally of itself by a shaft ll having toothed wheels l2 which engage perforations l3 along the margins of the sheet. The shaft H is driven by a suitable motor I4 which is controlled, as hereinafter described, to start and stop the movement of the chart as required.

The device is also provided with a sounddetecting means which likewise records the sounds upon the charts This sound recorder may be of anysuitable construction for the purpose. In the present case, it comprises a microphone or stethophone D of the type usually used, to be applied to the patients. arm adjacent the cuff to pick up the blood pressure sounds resulting from the excursion of the arterial walls when the cufl' is-inflated. The microphone operates through a suitable amplifier iii to energize a coil l6 carried upon a brass cylinder ll within which is positioned a permanent magnet I8. The cylinder is movable longitudinally of itself in response to the current impulses in the coil set up by the microphone, and these movements are transmitted to a pen marker l9 by the connecting link 20. The pen marker I9 is pivoted adjacent the margin of the chart and marks the coil movements representing the sound impulses as short, transverse lines along the margin of the chart.

The mechanisms described are all controlled automatically so that blood pressure can be taken at intervals over any extended period of time. The interval at which the blood pressure is to be recorded is determined by a multiple contact timing device. This consists of a cylinder 20 which is rotated by a suitable synchronous motor 2l, preferably at the rate of one revolution a minute. This cylinder carries several series of raised contacts-in the present case three serieswhich close a circuit to bring about the inflation of the cuff at the desired intervals, The contacts purpose of gradually reducing air pressure in the cufi from above the systolic'blood pressure to a 22 for 20-second intervals are three in number and are placed apart on'the cylinder; the contacts 22 for the 30-second intervals are two in number and are placed apart on thecylinder; and the contact 22' for the 1-minute intervals is a single contact. A brush 23 is provided for engaging these contacts in each of the series.

A selector switch 25 is provided, having a series of contacts 28 connected to the brushes 23, so that the operator, by setting the switch at any one of the contacts 24, can select the intervals at which the blood pressures are to be recorded. The contacts 23, 22', and 22 are of such length that as the cylinder rotates, the duration of engagement by the brushes 23 will be preferably four seconds, during which period the valve V is opened to admit air pressure to the cuff to inflate the cuff.

The source of power for operating the timer ,motor 2|, chart motor l4, and the valves V and V, is represented by the line conductors 30 and II, and the power supply for the relays and the electronic tube 4| is connected to this source of power and is conventionally indicated at 32. A main switch S is provided in the main line for starting and stopping the apparatus. Upon the closure of the main switch S, the timer motor 2| for cylinder 20 is started in rotation. The closure of the switch 8 also applies voltage from the power supply over conductor 34, relay R thyratron electronic tube 4i, conductor 42, to ground through contacts 35 and 38 of relay R The thyratron tube breaks down and allows current to flow in this circuit, which current energizes relay R. which opens the circuit of the chart motor l4 by separating the relay contacts 43-44, thereby stopping the chart motor or preventing it from running. Since the timer motor 2! and 'the contact cylinder 20 have started rotating,

the cylinder contacts are brought ,into contact with the brushes 23 which close a circuit to ground from the power supply 32 over conductor 33, which circuit includes relay R and the previously selected interval contact on the cylinder. The energization of relay R closes relay contacts 40 and 39, and closes a circuit which energizes valve magnet V of valve V The valve V is thereby opened to admit airunder pressure to the inflatable cuff 2. This valve remains open for the period of engagement of the brush 23 with the cylinder contact which, in the present instance, is four seconds, as before mentioned. The pressure reached in the cuff is determined by the manually operated pressure reducing valve 3.

At the end of the 4-second period, the cylinder contact leaves the brush 23 and opens the circuit, thus deenergizing relays R and restoring the movable contacts 35 and 40 to their initial positions in engagement with contacts 36 and 31, respectively, by virtue of springs or gravity, as well understood in connection with relays of this type, thus opening the relay contacts 35 and 31 and closing the contacts 35 and 36. The relay contacts 35 and 36 were separated during the 4- second inflation of the cuff, and the circuit through the thyratron tube 4| was interrupted. This de-energized relay R and restored the movable contact 43 to its initial position in engagement with contact 44 and movable contact 49 to its initial position out of engagement with contact 50, by virtue of springs or gravity, as well understood in connection with relays of this type. The de-energlzation of relay R brought together contacts 43 and 44 and separated contacts 49 and 50, thus de-energizing the operating magnet V of valve V so that the valve V remained closed.

When the relay contacts 35 and 31 were closed during the inflation of the cuff, a circuit was closed which included a. 3-microfarad condenser 45 which caused the condenser to charge to about 150 volts through a 100,000 ohm bleeder 46, so that upon the restoration of contacts 35 and 36 upon the de-energization of relay R the thyratron does not break down immediately because of the negative l50-volt charge applied by the condenser 45 to the grid 41 of the thyratron; instead, this charge gradually leaks through the 3 megohm variable resistor 43 which is bridged to ground across the condenser, and when the negative potential has decreased to about 6 volts the tube breaks down and allows current to flow in the circuit which includes the relay B. When the relay R was de-energized at the end of the 4-second period of inflation, the closing of relay contacts 40 and 38 completed the circuit for the chart motor l4 and started the movement of the chart C, relay R having become de-energized and permitting contacts 43 and 44 to close.

After the cuff has been inflated to a pressure wellabove the systolic blood pressure and the valve V closed, the air begins to leak out of the line and cuff through the adjustable bleeder valve V This gradually reduces the pressure in the cuff to a point below the diastolic blood pressure, the time occupied in reducing the pressure being regulated by adjusting the bleeder valve V accordingly. After the cuff pressure thus has been reduced below the diastolic blood pressure, it is thenv desirable to completely deflate the cuff of the remaining pressure before the next cycle of operation, and this is brought about by the 3 megohm variable resistor 48, above described, which serves as a timing device. the resistor the discharge of the condenser can be regulated to occupy any desired period of time in relation to the reduction of pressure in the cuff. If the blood pressure is to be taken periodically at 30-second intervals, for instance, it is desirable to provide a rest period of Say ten seconds during which the cuff pressure can be com pletely exhausted and the patient relieved of the discomfiture of cufif pressure until the next cycle of operation. Thus to allow a 10-second rest period before the next operation, the variable resistor 48 can accordingly be adjusted to time the discharge of the condenser and bring about the breakdown of the thyratron tube at the end of a 20-second period.

As before stated, when the thyratron breaks down and again-allows current to flow through relay R the energization of the relay R closes contacts 49 and 50, and this closes the circuit for the operating magnet V of valve V Valve V is thus opened and allows the remaining pressure in the cuff to quickly or suddenly exhaust to the atmosphere and thus completely deflate the cuff. The opening of the relay contacts 43 and 44 also opens the chart motor circuit and stops the movement of the chart C.

The cycle of operations is repeated when the next contact in the selected series on the rotating cylinder 20 engages the blush 23. The mechanism continues its interval operation for any desired length of time until stopped by opening the main switch S.

Referring now to Figs. 2 and 3, it will be observed that the chart C is provided with a series of longitudinal lines 5| which serve as calibrations for a series of figures representing pressure from 0 to 325 mm. Hg. The pen marker 5 makes a continuous curve or record on the chart, in response to the pressure conditions in the coil. The portion 52 of the curve represents the increase in pressure during the inflation of the cuff and while the chart is not moving; the portion 53 of the curve represents the gradual reduction in pressure in the cuff, this line being made By adjusting while the chart is moving; and the portion 54 of the curve represents the sudden and quick deflation of the cuff after the pressure has been reduced to a point below the diastolic pressure.

The blood pressure sounds are indicated by the marks 55 alone: the margin of the chart and are produced by the sounds resulting from the relationship between the cuff pressure and the blood pressure during the period when the nressure is being reduced in the cuff from above systolic to below diastolic blood pressure. In order to read the blood pressure from this record a separate device E, Figs. 3 and 4. is used. This device E com rises a flat base late 56 having guide rails 51 between which the chart. after it has been removed from the recorder. is moved and guided. This plate is bridged by a piece of transparent material 5I such as celluloid, and spaced above the plate suiflciently so that the chart can be easily moved along the base plate. The edge or margin 58 of the member 51 is arcuate. the arc of which corresponds to the arc of movement described by the pen marker.

' To read the record, the chart is shifted until its arcuate edge 58 intersects the portion 53 of the pressure curve and the sound marks on the margin of the chart. For instance. the curved broken line 59 representing the arc of the member E is shown on Fig. 2 as intersecting the first of a series of blood pressure sound marks 55 and the portion 53 of the pressure curve. This latter intersection indicates the systolic blood pressure. Likewise, the curved line 60 intersects the last of blood pressure sound marks and the portion 53 of the pressure curve, and indicates the diastolic pressure. For convenience in readin the record, the arcuate margin 58 is provided with a series of calibrations 6| which register with the lines 5| on the chart. Adjacent the arcuate margin 58, the celluloid member 5! has systolic blood pressure, a valve for providing a leak to gradually reduce the cuff pressure,'means for suddenly deflating the cuff, a timing device controlling the cuff-deflating means to deflate the cuff after the cuff pressure has been reduced below the diastolic blood pressure and prior to the next cuff inflation toprovide rest periods for the patient, said timing device including an electric circuit having therein a relay for controlling said cuff-deflating means and having therein an electronic tube controlling said relay, and means for determining the time of operation of said electronic tube.

2. In an automatic blood pressure recording device, the combination of an inflatable arm cuff and a source of compressed air therefor, means for periodically admitting air pressure to said mil to inflate the cuff at predetermined intervals, means for gradually reducing the pressure in said cuff, means for quickly deflating said cuff of the remaining pressure prior. to each next inflation of the cuff, and electrically operated.

means for controlling the operation of said cuflinflating means and said deflating means, said electrical means including an electronic tube and an adjustable resistor for timing the operation of said tube.

3. In an automatic blood pressure indicator, the combination of an inflatable arm cuff, a source of compressed air therefor, an electromagnetically operated valve for admitting air pressure to said cuff to inflate the cuff to a pressure above the systolic blood pressure, a second electromagnetically operated valve for exhausting said cuff of air pressure below the diastolic blood pressure, a bleeder valve for gradually reducing thecuff pressure to a point below the diastolic' blood pressure, a circuit controller for periodically energizing said first electromagnetic valve to inflate the cuff at regular intervals, an electronic tube for controlling the operation of said second electromagnetic valve to exhaust the cuff, and means for delaying the operation of said electronic tube for a portion oi. the time period between the cuff inflations.

4. In an automatic blood pressure indicator, the combination of an inflatable arm cuff, a source of compressed air, an electromagnetic valve for admitting air pressure to said cuff to inflate the cuff, a second electromagnetic valve for exhausting the pressure from said cuff, an electronic tube for controlling the operation of said second electromagneticvalve, a controller for periodically energizing said first electromagnetic valve and said electronic tubes at regular intervals, and an adjustable resistor for delaying the operation of said electronic tube after each energization thereof.

5. In an automatic blood pressure indicator, the combination of an inflatable arm cuff, means including an electromagnetically operated valve for periodically inflating the cuff at regular intervals to a pressure above the systolic blood pressure, a valve for providing a leak to gradually reduce the blood pressure, means for suddenly deflating the cuff, a timing device controlling the cuff deflating means to deflate the cuff after the cuff pressure has been reduced below the diastolic blood pressure and prior to the nextcuff inflation to provide rest periods for the patient, said timing device including an electric circuit having therein a relay for controlling said cuff deflating means and having therein an electronic tube controlling said relay, and an adjustable resistor for regulating the time of operation of said electronic tube after each cuff inflation.

6. In an automatic blood pressure indicator, the combination of an inflatable arm cuff and a source of compressed air therefor, an electromagnetically operated valve for admitting air pressure to said cuff to inflate the cuff, means for gradually reducing the pressure in said cuff, and a second electromagnetically operated valve for quickly deflating said cuff of remaining pres sure prior to each next inflation of the cuff, an electrically operated means for controlling the operation of said first and second electromagnetically operated'valves, said electrical means including an electronic tube, an adjustable resistor for timing the operation of said tube, and

.a controller for periodically energizing said first electromagnetic valve and said tube at regular intervals.

WARREN E. GILSON. 

